Oxidation of N-Boc-D-prolinol (I) with pyridinium dichromate affords aldehyde (II). This is subjected to Wittig condensation with methylene triphenylphosphorane to furnish N-Boc-2-vinylpyrrolidine (III). Hydroboration of (III) with 9-borabicyclononane, followed by oxidative work-up, leads to the primary alcohol (IV). Subsequent acidic Boc group cleavage in (IV) provides 2-pyrrolidinyl ethanol (V). Acylation of amine (V) with 4-methyl-3-nitrobenzenesulfonyl chloride (VI) gives sulfonamide (VII). The hydroxyl group of (VII) is further protected with methoxymethyl chloride, producing the methoxymethyl ether (VIII). Conversion of the ortho-nitrotoluene system (VIII) into indole (X) is then accomplished according to the Leimgruber-Batcho procedure, by condensation of (VIII) with dimethylformamide dimethylacetal, followed by reduction of the resultant nitro enamine (IX) with hydrazine in the presence of Raney nickel. Protection of the indole N of (X) with benzenesulfonyl chloride and NaH affords sulfonamide (XI). After acidic hydrolysis of the methoxymethyl protecting group of (XI), the N-phenylsulfonyl group is removed under alkaline conditions to yield indole (XII)
Conversion of alcohol (XII) into alkyl bromide (XIII) is carried out by treatment with carbon tetrabromide and triphenylphosphine. Then condensation of bromide (XIII) with 4-(4-chlorophenoxy)piperidine (XIV) in the presence of NaI and NaHCO3 produces the title compound